Tape reel and method for manufacturing the same

ABSTRACT

A tape reel according to the present invention includes: a disk-shape first flange having an opening in its central portion; a disk-shape second age having an opening in its central portion; and a cylindrical hub that includes, on an outer periphery thereof, a first pedestal for receiving the first flange and a second pedestal for receiving the second flange. The first flange and the second flange are joined to the first and second pedestals of the hub, respectively, and extend in a radial direction from the outer periphery of the hub. When viewed along a direction of a rotation axis of the reel, an outer periphery of the first pedestal and an outer periphery of the second pedestal are on circumferences of different concentric circles, and an upper surface of the first pedestal and an upper surface of the second pedestal face the same direction.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a tape reel that achieves high accuracyand a method for manufacturing the same.

2. Description of Related Art

In recent years, means for high-speed information transmission such asoptical fibers have made remarkable progress. As a result, it becamepossible to transmit images and data with an enormous amount ofinformation, while at the same time, there arises an increasing demandfor advanced techniques to record, reproduce, and store such images anddata. Examples of recording and reproducing media include flexibledisks, magnetic drums, hard disks, and magnetic tapes. Tape-shapedrecording media such as magnetic tapes play a major role mainly as databackup media, because their recording capacity per reel is large.Examples of the tape-shaped recording media include magnetic tapes andoptical tapes.

Usually, the tape-shaped recording medium is used in the state where itis wound around a reel and housed in a cartridge. Lately, with anincrease in recording capacity of a tape cartridge, further improvementin shape accuracy and rotational accuracy of a reel of the tapecartridge has been demanded.

The reel falls into two types, namely, a two-piece type and athree-piece type (see JP 10(1998)-320958 A and JP 2002-298542 A, forinstance). As shown in FIG. 9, a two-piece type reel 100 includes: a hub102 (a magnetic tape, for example, can be wound around an outerperipheral surface 101 of this hub 102); a disk-shape first flange 103that has an opening in its center and is fixed to the hub 102 bywelding; and a disk-shaped second age 104 that is formed integrally withthe hub 102. The first flange 103 can be joined to the hub 102 byultrasonic welding, caulking, or the like. Furthermore, as shown in FIG.10, when the reel 100 is in use, a magnetic tape 105 is wound around theouter peripheral surface 101 of the hub 102. As shown in FIGS. 11A and11B, the hub 102 as a component of the two-piece type reel is formedintegrally with the second flange 104, and the second flange 104 isformed so as to extend in the radial direction from an outer peripheryof the hub 102.

On the other hand, a three-piece type reel corresponds to, for example,the above-described two-piece type reel 100 in which the hub 102 and thesecond flange 104 are provided as separate components. In thethree-piece type reel, the first age, the hub, and the second flange arejoined to each other by ultrasonic welding, snap-fitting, or the like.

In both the two-piece type reel and the three-piece type reel, thecomponents thereof generally are manufactured by injection molding of aresin. In the two-piece type reel, the first flange and the hub providedwith the second flange are manufactured separately by injection molding.At this time, since the first flange has a flat disk shape, the resinflows smoothly during the injection molding, so that it is possible tomanufacture the first flange with high shape accuracy. In contrast, inthe hub provided with the second flange, the flange bends with respectto the tape-winding surface of the hub and the thickness of thetape-winding surface of the hub is different from that of the flange.Thus, when the resin flows during the injection molding, an internalpressure in the mold is liable to be nonuniform, which makes itdifficult to form the hub and the second flange integrally with highshape accuracy. Accordingly, the shape accuracy of the reel obtained byjoining these components also is deteriorated.

On the other hand, in the three-piece type reel, the first flange, thehub, and the second flange are manufactured separately by injectionmolding. The components of the three-piece type reel can be manufacturedwith higher shape accuracy as compared with the components of thetwo-piece type reel, because the components of the three-piece type reeldo not have a large bent portion and have a substantially uniformthickness. However, in order to manufacture the three-piece type reel,the flanges need to be joined to both sides of the hub, respectively.Thus, it is usually necessary to perform, after one of the flanges hasbeen joined to the hub, the step of turning over the hub to join theother flange, for example, thereby making the manufacturing processcomplicated. Also, a method of joining the flanges to both the sides ofthe hub, respectively, by snap-fitting has been proposed. However, whenthe flanges are joined by snap-fitting, each fitting portion needs tohave a clearance due to its construction, which poses a problem in thatthe components cannot be fixed together sufficiently after being joined,resulting in deteriorated shape accuracy of the reel as a whole.

When the shape accuracy of the reel is not sufficient as describedabove, the rotational accuracy of the reel also is deteriorated to makethe tape run unstable. This deteriorates the reading accuracy andrecording accuracy of recording signals by the drive head, therebycausing errors in reading and recording the recording signals.

SUMMARY OF THE INVENTION

The present invention is intended to solve the above-described problemsand to provide a tape reel that is of a three-piece type with eachcomponent having high shape accuracy and is improved in shape accuracyof the reel as a whole and a method for manufacturing such a tape reelefficiently.

A tape reel according to the present invention includes: a disk-shapefirst flange having an opening in its central portion; a disk-shapesecond flange having an opening in its central portion; and acylindrical hub that comprises, on an outer periphery thereof, a firstpedestal for receiving the first flange and a second pedestal forreceiving the second flange. The first flange and the second flange arejoined to the first and second pedestals of the hub, respectively, andextend in a radial direction from the outer periphery of the hub. Whenviewed along a direction of a rotation axis of the reel, an outerperiphery of the first pedestal and an outer periphery of the secondpedestal are on circumferences of different concentric circles, and anupper surface of the first pedestal and an upper surface of the secondpedestal face the same direction.

A method for manufacturing a tape reel according to the presentinvention is a method for manufacturing a tape reel that includes: adisk-shape first flange having an opening in its central portion; adisk-shape second flange having an opening in its central portion; and acylindrical hub that comprises, on an outer periphery thereof, a firstpedestal for receiving the first flange and a second pedestal forreceiving the second flange, wherein the first flange and the secondflange are joined to the first and second pedestals of the hub,respectively, and extend in a radial direction from the outer peripheryof the hub, when viewed along a direction of a rotation axis of thereel, an outer periphery of the first pedestal and an outer periphery ofthe second pedestal are on circumferences of different concentriccircles, and an upper surface of the first pedestal and an upper surfaceof the second pedestal face the same direction. The method includes thesteps of: joining the first flange to the first pedestal; and joiningthe second flange to the second pedestal.

Since the tape reel according to the present invention can achieve highshape accuracy, the rotational accuracy of the reel also is improved,which allows the running stability of the tape to be improved.

Moreover, by the method for manufacturing a tape reel according to thepresent invention, the above-described tape reel of the presentinvention can be manufactured efficiently with simple facilities.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a plan view showing an example of a first flange used in atape reel according to the present invention, FIG. 1B is a sectionalview taken along a line I-I in FIG. 1A, and FIG. 1C is an enlarged viewof a portion 1C in FIG. 1B.

FIG. 2A is a plan view showing an example of a second flange used in atape reel according to the present invention, FIG. 2B is a sectionalview taken along a line II-II in FIG. 2A, and FIG. 2C is an enlargedview of a portion 2C in FIG. 2B.

FIG. 3A is a plan view showing an example of a hub used in a tape reelaccording to the present invention, FIG. 3B is a side view of the same,FIG. 3C is a sectional view taken along a line III-III in FIG. 3A, andFIGS. 3D and 3E are enlarged views of portions 3D and 3E in FIG. 3C,respectively.

FIG. 4A is a sectional view showing an example of a tape reel accordingto the present invention, and FIGS. 4B and 4C are enlarged views ofportions 4B and 4C in FIG. 4A, respectively.

FIG. 5A is a sectional view illustrating an example of the step ofjoining the hub and the second flange, and FIG. 5B is an enlarged viewof a portion 5B in FIG. 5A.

FIG. 6A is a sectional view illustrating an example of the step ofjoining the hub and the first flange, and FIG. 6B is an enlarged view ofa portion 6B in FIG. 6A.

FIG. 7A is a sectional view showing another example of a tape reelaccording to the present invention, and FIGS. 7B and 7C are enlargedviews of portions 7B and 7C in FIG. 7A, respectively.

FIG. 8A is a sectional view showing still another example of a tape reelaccording to the present invention, and FIGS. 8B and 8C are enlargedviews of portions 8B and 8C in FIG. 8A, respectively.

FIG. 9 is a sectional view showing a conventional tape reel for amagnetic tape.

FIG. 10 is a sectional view showing the state where a tape is woundaround the tape reel shown in FIG. 9.

FIG. 11A is a plan view showing a hub used in the conventional tape reelfor a magnetic tape, and FIG. 11B is a side view of the same.

DETAILED DESCRIPTION OF THE INVENTION

The tape reel according to the present invention is a three-piece typetape reel including: a disk-shape first flange having an opening in itscentral portion: a cylindrical hub; and a disk-shape second flangehaving an opening in its central portion. The first flange and thesecond flange are joined to both sides of the hub, respectively, andextend in a radial direction from an outer periphery of the hub. Byconfiguring the tape reel so as to be a three-piece type tape reel, theshape accuracies of the respective components can be improved.

Furthermore, the hub include, on its outer periphery, a first pedestalfor receiving the first flange and a second pedestal for receiving thesecond flange. When viewed along a direction of a rotation axis of thereel, an outer periphery of the first pedestal and an outer periphery ofthe second pedestal are on circumferences of different concentriccircles, and an upper surface of the first pedestal and an upper surfaceof the second pedestal face the same direction. With this configuration,it becomes possible to join the first flange and the second flange tothe hub from the same direction (the uniaxial direction), which allowsan apparatus used for joining the hub and the flanges to be simplified.

Still further, the first flange is joined to the first pedestal, and thesecond flange is joined to the second pedestal. With this configuration,the flanges can be joined to the hub by ultrasonic welding, caulking,adhesion with the use of an adhering member, or the like, which allows aplurality of components to be fixed and joined with high accuracy.Accordingly the shape accuracy of the reel as a whole after therespective components have been joined also can be improved. It shouldbe noted that means for joining the hub and the flanges is not limitedto those described above, and any other means can be used as long as aplurality of components can be fixed and joined with high shapeaccuracy.

The tape reel according to the present invention is applicable not onlyto a single-reel type tape cartridge but also to a double-reel type tapecartridge. Moreover, the tape reel according to the present inventioncan be used not only as a reel of a tape cartridge but also as a reel ofa drive.

On the other hand, the method for manufacturing a tape reel according tothe present invention is a method for manufacturing the above-describedtape reel of the present invention. The method includes the steps ofjoining the first flange to the first pedestal; and joining the secondflange to the second pedestal. According to this method, it becomespossible to join the first flange and the second flange to the hub fromthe same direction (the uniaxial direction) as described above, therebyallowing a reel having high shape accuracy to be manufacturedefficiently. There is no particular limitation on the method of joiningthe hub and the flanges. However, methods of joining them by ultrasonicwelding, caulking, adhesion with the use of an adhering member, or thelike can fix and join a plurality of components with high accuracy andalso can improve the shape accuracy of the reel as a whole after therespective components have been joined.

Hereinafter, the present invention will be described by way ofillustrative embodiments with reference to the drawings.

Embodiment 1

FIG. 1A is a plan view showing an example of a first flange used in atape reel according to the present invention, and FIG. 1B is a sectionalview taken along a line I-I in FIG. 1A. As shown in FIGS. 1A and 1B, afirst flange 10 is formed in a disk shape with an opening 11 in itscentral portion. FIG. 1C is an enlarged view of a portion 1C in FIG. 1B.As shown in FIG. 1C, the first flange 10 has a joining rib 12 providedon its inner periphery. On the tip end of the joining rib 12, a weldingprojection 13 is provided. Furthermore, the first flange 10 has a rib 14provided on its inner periphery on the side opposite to the joining rib12. As the material of the first flange 10, resins can be used. In thiscase, since the first flange 10 has a substantially flat disk shape, theresin can be caused to flow with a uniform internal pressure at the timeof injection molding, so that the shape of the first flange 10 can beformed with high accuracy. It is to be noted that the material of thefirst flange 10 is not limited to resins as long as the first flange 10can be joined to other components.

FIG. 2A is a plan view showing an example of a second flange used in atape reel according to the present invention, and FIG. 2B is a sectionalview taken along a line II-II in FIG. 2A. As shown in FIGS. 2A and 2B, asecond flange 20 is formed in a disk shape with an opening 21 in itscentral portion. FIG. 2C is an enlarged view of a portion 2C in FIG. 2B.As shown in FIG. 2C, the second flange 20 has a joining rib 22 providedon its inner periphery. On the tip end of the joining rib 22, a weldingprojection 23 is provided. As the material of the second flange 20,resins can be used In this case, since the second flange 20 has asubstantially flat disk shape, the resin can be caused to flow with auniform internal pressure at the time of injection molding so that theshape of the second flange 20 can be formed with high accuracy. It is tobe noted that the material of the second flange 20 is not limited toresins as long as the second flange 20 can be joined to othercomponents.

FIG. 3A is a plan view showing an example of a hub used in a tape reelaccording to the present invention, FIG. 3B is a side view of the same,and FIG. 3C is a sectional view taken along a line III-III in FIG. 3A.As shown in FIGS. 3A to 3C, a hub 30 is formed in a bottomed cylindricalshape. The hub 30 includes, on its outer periphery, a first pedestal 31for receiving the above-described first flange 10 (FIG. 1A) and a secondpedestal 32 for receiving the above-described second flange 20 (FIG.2A). When viewed along the direction of a rotation axis 33 of the reel,an outer periphery 31 a of the first pedestal 31 and an outer periphery32 a of the second pedestal 32 are on circumferences of differentconcentric circles, and an outer diameter of the first pedestal 31 isset to be smaller than that of the second pedestal 32. Furthermore, anupper surface 31 b of the first pedestal 31 and an upper surface 32 b ofthe second pedestal 32 both face the same direction (they face upward inFIG. 3B). FIGS. 3D and 3E are enlarged views of portions 3D and 3E inFIG. 3C, respectively. As shown in FIG. 3D, the first pedestal 31 has ajoining groove 34, and as shown in FIG. 3E, the second pedestal 32 has ajoining groove 35. As the material of the hub 30, resins can be used. Inthis case, since the hub 30 has no flange portion, the resin can becaused to flow with a uniform internal pressure at the time of injectionmolding, in contrast to the case of a conventional hub provided withflanges. Thus, the shape of the hub 30 can be formed with high accuracy.It is to be noted that the material of the hub 30 is not limited toresins as long as the hub 30 can be joined to other components.

FIG. 4A is a sectional view showing an example of a tape reel accordingto the present invention. As shown in FIG. 4A, a reel 40 is formed byjoining the first flange 10, the second flange 20, and the hub 30, whichhave been described with reference to FIGS. 1A to 3E above. FIGS. 4B and4C are enlarged views of portions 4B and 4C in FIG. 4A, respectively. Asshown in FIG. 4B, the joining rib 12 of the first flange 10 is joined tothe joining groove 34 of the first pedestal 31 by ultrasonic weldingthat will be described later, and as shown in FIG. 4C, the joining rib22 of the second flange 20 is joined to the joining groove 35 of thesecond pedestal 32 by ultrasonic welding that will be described later.

Next, a method for manufacturing the tape reel according to the presentembodiment will be described. FIG. 5A is a sectional view illustratingan example of the step of joining the hub and the second flange, andFIG. 5B is an enlarged view of a portion 5B in FIG. 5A. FIG. 6A is asectional view illustrating an example of the step of joining the huband the first flange, and FIG. 6B is an enlarged view of a portion 6B inFIG. 6A. Note here that, in FIGS. 5 and 6, components other than the huband the flanges are not shown in cross section.

First, as shown in FIGS. 5A and 5B, the hub 30 is fixed to a receivingjig 50 that is formed in a protruding shape. Thereafter, the secondflange 20 is placed on the second pedestal 32 from above, and thejoining rib 22 of the second flange 20 is inserted into the joininggroove 35 of the second pedestal 32. Then, a first welding horn 51 isplaced on the side opposite to the joining rib 22 of the second flange20 such that a portion to be joined is sandwiched between the firstwelding horn 51 and the receiving jig 50. Finally, the first weldinghorn 51 applies an ultrasonic wave to the portion to be joined to meltthe welding projection 23 of the joining rib 22, thereby welding thejoining rib 22 to the joining groove 35. By this first step, the secondflange 20 can be joined and fixed to the hub 30 with high shapeaccuracy.

Next, as shown in FIGS. 6A and 6B, the first flange 10 is placed on thefirst pedestal 31 from above, and the joining rib 12 of the first flange10 is inserted into the joining groove 34 of the first pedestal 31.Then, a second welding horn 52 is placed on the rib 14 of the firstflange 10 such that a portion to be joined is sandwiched between thesecond welding horn 52 and the receiving jig 50. Finally, the secondwelding horn 52 applies an ultrasonic wave to the portion to be joinedto melt the welding projection 13 of the joining rib 12, thereby weldingthe joining rib 12 to the joining groove 34. By this second step, thefirst flange 10 can be joined and fixed to the hub 30 with high shapeaccuracy.

According to the manufacturing method of the present embodiment, thefirst flange 10 and the second flange 20 can be placed on the hub 30from the same direction, so that it is possible to join the first flange10 and the second flange 20 without turning over the hub 30. Thus, anapparatus used for joining can be simplified and the joining process canbe carried out efficiently.

Furthermore, in the first and second steps described above, bysandwiching the portion to be joined between the first and secondwelding horns 51, 52 and the receiving jig 50, the loss in weldingenergy can be suppressed and the welding accuracy can be improved. Notehere that a common horn may be used as the first welding horn 51 and thesecond welding horn 52 in the first and second steps.

Embodiment 2

FIG. 7A is a sectional view showing another example of a tape reelaccording to the present invention. As shown in FIG. 7A, a reel 60 isformed by joining a first flange 15, a second flange 20, and a hub 36.The first flange 15 is formed in a disk shape with an opening in itscentral portion and has a pass-through slit 16 for caulking on its innerperiphery. The second flange 20 has the same configuration as that usedin Embodiment 1. Thus, in the following, the same components are giventhe same reference numerals and the description thereof has beenomitted. Furthermore, the hub 36 has the same configuration as the hub30 used in Embodiment 1 except that a caulking boss 37 is providedinstead of the joining groove 34 (FIG. 3D). Thus, in the following, thesame components are given the same reference numerals and thedescription thereof has been omitted.

FIGS. 7B and 7C are enlarged views of portions 7B and 7C in FIG. 7A,respectively. As shown in FIG. 7B, the first flange 15 is joined to afirst pedestal 31 of the hub 36 by caulking via the caulking boss 37. Asshown in FIG. 7C, a joining rib 22 of the second flange 20 is joined toa joining groove 35 of a second pedestal 32 by ultrasonic welding, as inEmbodiment 1. The reason why only the first flange 15 is joined bycaulking in the present embodiment is that, even if the first flange 15is joined by caulking, the caulking boss 37 does not interfere with thetape-winding surface. On the other hand, if the second flange 20 isjoined by caulking, a caulking boss sticks out so as to interfere withthe tape-winding surface, thus hindering the tape winding.

The tape reel 60 of the present embodiment has substantially the sameconfiguration as the tape reel 40 of Embodiment 1 except that the firstflange 15 and the hub 36 are joined by caulking and produces the sameeffect as the tape reel 40 of Embodiment 1. Moreover, according to amethod for manufacturing the tape reel 60 of the present embodiment, thefirst flange 15 and the second flange 20 can be placed on the hub 36from the same direction, so that it is possible to join the first flange15 and the second flange 20 without turning over the hub 36; Thus, anapparatus used for joining can be simplified and the joining process canbe carried out efficiently.

Embodiment 3

FIG. 8A is a sectional view showing still another example of a tape reelaccording to the present invention. As shown in FIG. 8A, a reel 70 isformed by joining a first flange 80, a second flange 25, and a hub 30.The first flange 80 is formed in a disk shape with an opening in itscentral portion and has a rib 81 on its inner periphery. The secondflange 25 has the same configuration as the second flange 20 used inEmbodiment 1 except that the joining rib 22 (FIG. 2C) is not provided,and thus the description thereof has been omitted. Furthermore, the hub30 has the same configuration as that used in Embodiment 1. Thus, in thefollowing, the same components are given the same reference numerals andthe description thereof has been omitted.

FIGS. 8B and 8C are enlarged views of portions 8B and 8C in FIG. 8A,respectively. As shown in FIGS. 8B and 8C, each of a joining groove 34and a joining groove 35 of the hub 30 is filled with an adhesive 82, sothat the first flange 80 is joined to a first pedestal 31 of the hub 30with the adhesive 82 and the second flange 25 is joined to a secondpedestal 32 of the hub 30 with the adhesive 82. There is no particularlimitation on the adhesive 82, and ultraviolet-curing resins and thelike can be used as the adhesive 82.

The tape reel 70 of the present embodiment has substantially the sameconfiguration as the tape reel 40 of Embodiment 1 except that the firstflange 80 and the second flange 25 are joined to the hub 30 with theadhesive 82 and produces the same effect as the tape reel 40 ofEmbodiment 1. Moreover, according to a method for manufacturing the tapereel 70 of the present embodiment, the first flange 80 and the secondflange 25 can be placed on the hub 30 from the same direction, so thatit is possible to join the first flange 80 and the second flange 25without turning over the hub 30. Thus, an apparatus used for joining canbe simplified and the joining process can be carried out efficiently.

As specifically described above, since the tape reel according to thepresent invention can achieve high shape accuracy, the rotationalaccuracy of the reel also is improved, which allows the runningstability of the tape to be improved. Consequently, the tape reelaccording to the present invention can contribute to higher performanceof tape cartridges.

Moreover, by the method for manufacturing a tape reel according to thepresent invention, the above-described tape reel of the presentinvention can be manufactured efficiently with simple facilities. Thus,the method according to the present invention is extremely valuable froman industrial viewpoint.

The invention may be embodied in other forms without departing from thespirit or essential characteristics thereof. The embodiments disclosedin this application are to be considered in all respects as illustrativeand not limiting. The scope of the invention is indicated by theappended claims rather than by the foregoing description, and allchanges which come within the meaning and range of equivalency of theclaims are intended to be embraced therein.

1. A tape reel comprising: a disk-shape first flange having an openingin its central portion; a disk-shape second flange having an opening inits central portion; and a cylindrical hub that comprises, on an outerperiphery thereof, a first pedestal for receiving the first flange and asecond pedestal for receiving the second flange, wherein the firstflange and the second flange are joined to the first and secondpedestals of the hub, respectively, and extend in a radial directionfrom the outer periphery of the hub, when viewed along a direction of arotation axis of the reel, an outer periphery of the first pedestal andan outer periphery of the second pedestal are on circumferences ofdifferent concentric circles, and an upper surface of the first pedestaland an upper surface of the second pedestal face the same direction. 2.The tape reel according to claim 1, wherein an outer diameter of thefirst pedestal is smaller than an outer diameter of the second pedestal,each of the first flange and the second flange has a joining rib on itsinner periphery, each of the first pedestal and the second pedestal hasa joining groove, the joining rib of the first flange is joined to thejoining groove of the first pedestal by ultrasonic welding, and thejoining rib of the second flange is joined to the joining groove of thesecond pedestal by ultrasonic welding.
 3. The tape reel according toclaim 2, wherein a welding projection is provided on a tip end of thejoining rib of each of the first flange and the second flange.
 4. Thetape reel according to claim 1, wherein an outer diameter of the firstpedestal is smaller than an outer diameter of the second pedestal, thefirst flange is joined to the first pedestal by caulking, and the secondflange is joined to the second pedestal by ultrasonic welding.
 5. Thetape reel according to claim 1, wherein an outer diameter of the firstpedestal is smaller than an outer diameter of the second pedestal, thefirst flange is joined to the first pedestal with an adhering member,and the second flange is joined to the second pedestal with an adheringmember.
 6. A method for manufacturing a tape reel, the tape reelcomprising: a disk-shape first flange having an opening in its centralportion; a disk-shape second flange having an opening in its centralportion; and a cylindrical hub that comprises, on an outer peripherythereof, a first pedestal for receiving the first flange and a secondpedestal for receiving the second flange, wherein the first flange andthe second flange are joined to the first and second pedestals of thehub, respectively, and extend in a radial direction from the outerperiphery of the hub, when viewed along a direction of a rotation axisof the reel, an outer periphery of the first pedestal and an outerperiphery of the second pedestal are on circumferences of differentconcentric circles, and an upper surface of the first pedestal and anupper surface of the second pedestal face the same direction, the methodcomprising the steps of: joining the first flange to the first pedestal;and joining the second flange to the second pedestal.
 7. The methodaccording to claim 6, wherein an outer diameter of the first pedestal issmaller than an outer diameter of the second pedestal, each of the firstflange and the second flange has a joining rib on its inner periphery,each of the first pedestal and the second pedestal has a joining groove,the joining rib of the first flange is joined to the joining groove ofthe first pedestal by ultrasonic welding, and the joining rib of thesecond flange is joined to the joining groove of the second pedestal byultrasonic welding.
 8. The method according to claim 6, wherein an outerdiameter of the first pedestal is smaller than an outer diameter of thesecond pedestal, the first flange is joined to the first pedestal bycaulking, and the second flange is joined to the second pedestal byultrasonic welding.
 9. The method according to claim 6, wherein an outerdiameter of the first pedestal is smaller than an outer diameter of thesecond pedestal, the first flange is joined to the first pedestal withan adhering member, and the second flange is joined to the secondpedestal with an adhering member.